<?php
/**
 * CFileCache class file
 *
 * @author Qiang Xue <qiang.xue@gmail.com>
 * @link http://www.yiiframework.com/
 * @copyright Copyright &copy; 2008-2011 Yii Software LLC
 * @license http://www.yiiframework.com/license/
 */

/**
 * CFileCache provides a file-based caching mechanism.
 *
 * For each data value being cached, CFileCache will use store it in a separate file
 * under {@link cachePath} which defaults to 'protected/runtime/cache'.
 * CFileCache will perform garbage collection automatically to remove expired cache files.
 *
 * See {@link CCache} manual for common cache operations that are supported by CFileCache.
 *
 * @author Qiang Xue <qiang.xue@gmail.com>
 * @version $Id: CFileCache.php 3300 2011-06-23 14:29:56Z qiang.xue $
 * @package system.caching
 * @since 1.0.6
 */
class CFileCache extends CCache
{
    /**
     * @var string the directory to store cache files. Defaults to null, meaning
     * using 'protected/runtime/cache' as the directory.
     */
    public $cachePath;
    /**
     * @var string cache file suffix. Defaults to '.bin'.
     */
    public $cacheFileSuffix='.bin';
    /**
     * @var integer the level of sub-directories to store cache files. Defaults to 0,
     * meaning no sub-directories. If the system has huge number of cache files (e.g. 10K+),
     * you may want to set this value to be 1 or 2 so that the file system is not over burdened.
     * The value of this property should not exceed 16 (less than 3 is recommended).
     */
    public $directoryLevel=0;

    private $_gcProbability=100;
    private $_gced=false;

    /**
     * Initializes this application component.
     * This method is required by the {@link IApplicationComponent} interface.
     * It checks the availability of memcache.
     * @throws CException if APC cache extension is not loaded or is disabled.
     */
    public function init()
    {
        parent::init();
        if($this->cachePath===null)
        $this->cachePath=Yii::app()->getRuntimePath().DIRECTORY_SEPARATOR.'cache';
        if(!is_dir($this->cachePath))
        mkdir($this->cachePath,0777,true);
    }

    /**
     * @return integer the probability (parts per million) that garbage collection (GC) should be performed
     * when storing a piece of data in the cache. Defaults to 100, meaning 0.01% chance.
     */
    public function getGCProbability()
    {
        return $this->_gcProbability;
    }

    /**
     * @param integer $value the probability (parts per million) that garbage collection (GC) should be performed
     * when storing a piece of data in the cache. Defaults to 100, meaning 0.01% chance.
     * This number should be between 0 and 1000000. A value 0 meaning no GC will be performed at all.
     */
    public function setGCProbability($value)
    {
        $value=(int)$value;
        if($value<0)
        $value=0;
        if($value>1000000)
        $value=1000000;
        $this->_gcProbability=$value;
    }

    /**
     * Deletes all values from cache.
     * This is the implementation of the method declared in the parent class.
     * @return boolean whether the flush operation was successful.
     * @since 1.1.5
     */
    protected function flushValues()
    {
        $this->gc(false);
        return true;
    }

    /**
     * Retrieves a value from cache with a specified key.
     * This is the implementation of the method declared in the parent class.
     * @param string $key a unique key identifying the cached value
     * @return string the value stored in cache, false if the value is not in the cache or expired.
     */
    protected function getValue($key)
    {
        $cacheFile=$this->getCacheFile($key);
        if(($time=@filemtime($cacheFile))>time())
        return file_get_contents($cacheFile);
        else if($time>0)
        @unlink($cacheFile);
        return false;
    }

    /**
     * Stores a value identified by a key in cache.
     * This is the implementation of the method declared in the parent class.
     *
     * @param string $key the key identifying the value to be cached
     * @param string $value the value to be cached
     * @param integer $expire the number of seconds in which the cached value will expire. 0 means never expire.
     * @return boolean true if the value is successfully stored into cache, false otherwise
     */
    protected function setValue($key,$value,$expire)
    {
        if(!$this->_gced && mt_rand(0,1000000)<$this->_gcProbability)
        {
            $this->gc();
            $this->_gced=true;
        }

        if($expire<=0)
        $expire=31536000; // 1 year
        $expire+=time();

        $cacheFile=$this->getCacheFile($key);
        if($this->directoryLevel>0)
        @mkdir(dirname($cacheFile),0777,true);
        if(@file_put_contents($cacheFile,$value,LOCK_EX)!==false)
        {
            @chmod($cacheFile,0777);
            return @touch($cacheFile,$expire);
        }
        else
        return false;
    }

    /**
     * Stores a value identified by a key into cache if the cache does not contain this key.
     * This is the implementation of the method declared in the parent class.
     *
     * @param string $key the key identifying the value to be cached
     * @param string $value the value to be cached
     * @param integer $expire the number of seconds in which the cached value will expire. 0 means never expire.
     * @return boolean true if the value is successfully stored into cache, false otherwise
     */
    protected function addValue($key,$value,$expire)
    {
        $cacheFile=$this->getCacheFile($key);
        if(@filemtime($cacheFile)>time())
        return false;
        return $this->setValue($key,$value,$expire);
    }

    /**
     * Deletes a value with the specified key from cache
     * This is the implementation of the method declared in the parent class.
     * @param string $key the key of the value to be deleted
     * @return boolean if no error happens during deletion
     */
    protected function deleteValue($key)
    {
        $cacheFile=$this->getCacheFile($key);
        return @unlink($cacheFile);
    }

    /**
     * Returns the cache file path given the cache key.
     * @param string $key cache key
     * @return string the cache file path
     */
    protected function getCacheFile($key)
    {
        if($this->directoryLevel>0)
        {
            $base=$this->cachePath;
            for($i=0;$i<$this->directoryLevel;++$i)
            {
                if(($prefix=substr($key,$i+$i,2))!==false)
                $base.=DIRECTORY_SEPARATOR.$prefix;
            }
            return $base.DIRECTORY_SEPARATOR.$key.$this->cacheFileSuffix;
        }
        else
        return $this->cachePath.DIRECTORY_SEPARATOR.$key.$this->cacheFileSuffix;
    }

    /**
     * Removes expired cache files.
     * @param boolean $expiredOnly whether to removed expired cache files only. If true, all cache files under {@link cachePath} will be removed.
     * @param string $path the path to clean with. If null, it will be {@link cachePath}.
     */
    public function gc($expiredOnly=true,$path=null)
    {
        if($path===null)
        $path=$this->cachePath;
        if(($handle=opendir($path))===false)
        return;
        while(($file=readdir($handle))!==false)
        {
            if($file[0]==='.')
            continue;
            $fullPath=$path.DIRECTORY_SEPARATOR.$file;
            if(is_dir($fullPath))
            $this->gc($expiredOnly,$fullPath);
            else if($expiredOnly && @filemtime($fullPath)<time() || !$expiredOnly)
            @unlink($fullPath);
        }
        closedir($handle);
    }
}
